This invention relates to a liquid ejecting apparatus for ejecting a drop of liquid from a nozzle. In particular, this invention is related to a liquid ejecting apparatus for ejecting a plurality of drops of liquid from a nozzle wherein respective volumes of the plurality of drops of liquid may be different.
In a ink-jetting recording apparatus such as an ink-jetting printer or an ink-jetting plotter (a kind of liquid ejecting apparatus), a recording head (head member) is caused to move in a main scanning direction, and a recording paper (a kind of printing-recording medium) is caused to move in a sub-scanning direction. In cooperation with those movements, a drop of ink can be ejected from a nozzle of the recording head onto the recording paper. Thus, an image (character) can be recorded on the recording paper. For example, the drop of ink can be ejected by causing a pressure chamber communicating with the nozzle to expand and/or contract.
The pressure chamber may be caused to expand and/or contract, for example by utilizing deformation of a piezoelectric vibrating member. In such a recording head, the piezoelectric vibrating member can be deformed based on a supplied driving-pulse in order to change a volume of the pressure chamber. When the volume of the pressure chamber is changed, a pressure of the ink in the pressure chamber may be changed. Then, the drop of ink is ejected from the nozzle.
In such a recording apparatus, a driving signal consisting of a series of a plurality of driving-pulses is generated. On the other hand, printing data (ejecting data) including level (gradation) information can be transmitted to the recording head. Then, based on the transmitted printing data, only necessary one or more driving-pulses are selected from the driving signal and supplied to the piezoelectric vibrating member. Thus, a volume of the ink ejected from the nozzle may be changed based on the level information.
In detail, for example, in an ink-jetting printer used with four level data consisting of: printing data for no recording (level information 00), printing data for a small dot (level information 01), printing data for a middle dot (level information 10) and printing data for a large dot (level information 11), respective volumes of the ink corresponding to the respective level information may be ejected.
In order to achieve the above four-level recording, for example, a driving signal shown in FIG. 18 may be used. As shown in FIG. 18, the driving signal has a first pulse signal PAPS1 arranged in a term PAT1, a second pulse signal PAPS2 arranged in a term PAT2 and a third pulse signal PAPS3 arranged in a term PAT3, which are connected in a series manner. The driving signal is a pulse-row signal having a recording period PATA.
In the case, the first pulse signal PAPS1 is adapted to function as a first driving pulse PADP1. The second pulse signal PAPS2 is adapted to function as a second driving pulse PADP2. The third pulse signal PAPS3 is adapted to function as a third driving pulse PADP3.
The first driving pulse PADP1, the second driving pulse PADP2 and the third driving pulse PADP3 have a common wave-pattern (wave form). Each of them can eject a drop of the ink alone. That is, when each of the driving pulses is supplied to the piezoelectric vibrating member, a drop of the ink, whose volume corresponds to a small dot, is ejected from the nozzle.
In the case, as shown in FIG. 19, a level control can be achieved by increasing or decreasing the number of the driving pulses supplied to the piezo electric vibrating member. For example, when only one driving pulse is supplied to the piezoelectric vibrating member, a small dot recording is achieved. When only two driving pulses are supplied to the piezoelectric vibrating member, a middle dot recording is achieved. When the three driving pulses are supplied to the piezoelectric vibrating member, a large dot recording is achieved.
Prior to this invention, a Japanese Patent Application No. 2001-194025 has been filed. The invention disclosed in the specification thereof relates to a technique to eject ink in order to print an image on a printing medium.
When a line drawing such as a character or an illustration is printed by means of an ink-jetting printer, bleeding of the ink may be generated at a contour portion of the line drawing. Such bleeding of the ink may be caused because the ink ejected at the line-drawing area is not fully absorbed by the printing medium and hence forms an ink pool, and then the ink of the ink pool starts to flow toward another area wherein no ink dot is to be formed.
The object of the above invention is to restrain bleeding of ink at a contour portion, in a printing apparatus that ejects drops of the ink in order to print an image.
In a printing apparatus according to the above invention, a contour is extracted, and volumes of ink for dots formed in pixels adjacent to the contour are regularly reduced. Thus, bleeding of the ink can be restrained, particularly when a text is printed on a printing paper such as a normal paper whose capacity to absorb the ink is small.
The reduction of the volumes of ink may be conducted by culling dots or by forming smaller dots.
In addition, in the invention disclosed in the Japanese Patent Application No. 2001-194025, the manner of reducing the volumes of the ink is fixed for the pixels adjacent to the contour. For example, when the driving signal shown in FIG. 18 is used, a small dot is formed in each pixel adjacent to the contour. As shown in FIG. 19, the small dot is formed by selecting the central driving pulse.
Thus, for example, if a large alphabet xe2x80x9cHxe2x80x9d is printed, drops of the ink are ejected at edge portions as shown in FIG. 20.
However, the inventor has found that gap lines Gin FIG. 20 can be easily perceived by human eyes, unexpectedly. Especially, in a case wherein BK (black) ink is used, existence of the gap lines G may be desight (eyesore) extremely. In order to achieve printing with much higher quality, it may be effective to restrain the gap lines G from being generated.
The object of this invention is to solve the above problems, that is, to provide a liquid ejecting apparatus such as an ink-jet recording apparatus that can achieve an edge process to prevent bleeding of ink and that can restrain generation of a gap line perceived at an edge portion.
This invention is a liquid ejecting apparatus comprising: a head having a nozzle; a main scanning unit that causes the head member to move in a main scanning direction relatively to a recording medium; a pressure-changing unit that causes pressure of liquid in the nozzle to change; a level-data setting unit that sets a selected level data from a plurality of level data, based on each of ejecting data forming a row corresponding to a main scanning movement; a driving-signal generator that generates an ejecting-driving signal; a driving-pulse generator that generates a driving pulse based on the selected level data and the ejecting-driving signal; and a main controller that causes the pressure-changing unit to operate, based on the driving pulse; wherein the row of the ejecting data includes: ejecting-sequential data corresponding to a continuous area of level data of relatively high density, an anterior edge data preceding the continuous area, and a posterior edge data following the continuous area; the level-data setting unit is adapted to set a selected level data of relatively high density based on each of the ejecting-sequential data, to set a selected level data of relatively low density based on the anterior edge data, and to set a selected level data of relatively low density based on the posterior edge data.
According to the invention, setting of level data based on the anterior edge data and setting of level data based on the posterior edge data can be independently conducted. Thus, for example, the manner of ejecting the liquid based on the anterior edge data may be made different from the manner of ejecting the liquid based on the posterior edge data. Thus, it is possible to restrain generation of a gap line that can be perceived at an edge portion.
For example, the ejecting-driving signal is a periodical signal including a plurality of pulse-waves. In the case, for example, the driving-pulse generator is adapted to generate a rectangular-pulse row corresponding to a period of the ejecting-driving signal based on the selected level data, and generate an AND signal of the rectangular-pulse row and the ejecting-driving signal as the driving pulse.
In a preferable concrete example, the plurality of level data include a first low-density level data and a second low-density level data; the level-data setting unit is adapted to set the first low-density level data based on the anterior edge data, and to set the second low-density level data based on the posterior edge data; and the ejecting-driving signal is a periodical signal including: a first small-dot pulse-wave that is for ejecting a small drop of the liquid from the nozzle, a second small-dot pulse-wave that is for ejecting a small drop of the liquid from the nozzle, and a third pulse-wave arranged between the first small-dot pulse-wave and the second small-dot pulse-wave, in each period thereof. Then, the driving-pulse generator is adapted to generate, based on the ejecting-driving signal: a driving-pulse including only the second small-dot pulse-wave when the selected level data is the first low-density level data, and a driving-pulse including only the first small-dot pulse-wave when the selected level data is the second low-density level data.
According to the above feature, both the small drop of the liquid ejected based on the anterior edge data and the small drop of the liquid ejected based on the posterior edge data become closer to the continuous area. Thus, it is possible to much effectively restrain generation of a gap line that can be perceived at an edge portion.
In general, it is preferable that the small drop of the liquid ejected from the nozzle according to the first small-dot pulse-wave has the same volume as the small drop of the liquid ejected from the nozzle according to the second small-dot pulse-wave. In the case, in general, the first small-dot pulse-wave and the second small-dot pulse-wave have the same wave-pattern (wave form).
In addition, in the case, preferably, the plurality of level data further include a high-density level data, the level-data setting unit is adapted to set the high-density level data based on each of the ejecting-sequential data, and the driving-pulse generator is adapted to generate a driving-pulse including at least the third pulse-wave when the selected level data is the high-density level data, based on the ejecting-driving signal. For example, the driving-pulse generator is adapted to generate a driving-pulse including the first small-dot pulse-wave, the second small-dot pulse-wave and the third pulse-wave, when the selected level data is the high-density level data, based on the ejecting-driving signal. The third pulse-wave may have the same wave-pattern as the first small-dot pulse-wave and the second small-dot pulse-wave, or may have a different wave-pattern from those.
In addition, it is preferable that the liquid ejecting apparatus further comprises a sub scanning unit that causes the head member to move in a sub scanning direction perpendicular to the main scanning direction relatively to the recording medium. In the case, the row of the ejecting data may include a longitudinal edge data adjacent to the continuous area of level data of relatively high density in the sub scanning direction. Then, it is preferable that the level-data setting unit is adapted to set the first low-density level data or the second low-density level data based on the longitudinal edge data.
Concretely, for example, when only two longitudinal edge data are serial in the main scanning direction, the level-data setting unit is adapted to set the first low-density level data based on the former longitudinal edge data, and to set the second low-density level data based on the latter longitudinal edge data.
Alternatively, when an even number of longitudinal edge data are serial in the main scanning direction, the level-data setting unit is adapted to set the first low-density level data based on each of former half of the longitudinal edge data, and to set the second low-density level data based on each of latter half of the longitudinal edge data.
More preferably, the plurality of level data further include a zero level data that corresponds to non-ejecting of the liquid, the driving-pulse generator is adapted to generate a driving-pulse not including any pulse-wave that is for ejecting a drop of the liquid when the selected level data is the zero level data, based on the ejecting-driving signal, and the level-data setting unit is adapted to set the first low-density level data, the second low-density level data or the zero level data, based on the longitudinal edge data.
Concretely, for example, when only three longitudinal edge data are serial in the main scanning direction, the level-data setting unit is adapted to set the first low-density level data based on the former longitudinal edge data, to set the zero level data based on the central longitudinal edge data, and to set the second low-density level data based on the latter longitudinal edge data.
Alternatively, when an odd number of longitudinal edge data are serial in the main scanning direction, the level-data setting unit is adapted to set the zero level data based on the central longitudinal edge data, to set the first low-density level data based on each of former longitudinal edge data with respect to the central longitudinal edge data, and to set the second low-density level data based on each of latter longitudinal edge data with respect to the central longitudinal edge data.
Alternatively, when only two longitudinal edge data are serial in the main scanning direction, the level-data setting unit is adapted to select one from the former longitudinal edge data and the latter longitudinal edge data; if the level-data setting unit selects the former longitudinal edge data, the level-data setting unit is adapted to set the first low-density level data based on the former longitudinal edge data; if the level-data setting unit selects the latter longitudinal edge data, the level-data setting unit is adapted to set the second low-density level data based on the latter longitudinal edge data; and the level-data setting unit is adapted to set the zero level data based on the unselected one of the former longitudinal edge data and the latter longitudinal edge data.
Alternatively, when an even number of longitudinal edge data are serial in the main scanning direction, the level-data setting unit is adapted to select one from the central two of the longitudinal edge data; if the level-data setting unit selects the former longitudinal edge data from the central two longitudinal edge data, the level-data setting unit is adapted to set the first low-density level data based on the former longitudinal edge data; if the level-data setting unit selects the latter longitudinal edge data from the central two longitudinal edge data, the level-data setting unit is adapted to set the second low-density level data based on the latter longitudinal edge data; the level-data setting unit is adapted to set the zero level data based on the unselected one of the central two longitudinal edge data; and the level-data setting unit is adapted to set the first low-density level data based on each of former longitudinal edge data with respect to the central two longitudinal edge data, and to set the second low-density level data based on each of latter longitudinal edge data with respect to the central two longitudinal edge data.
In addition, this invention is a controlling unit for controlling a liquid ejecting apparatus including: a head having a nozzle, a main scanning unit that causes the head member to move in a main scanning direction relatively to a recording medium, and a pressure-changing unit that causes pressure of liquid in the nozzle to change, the controlling unit comprising: a level-data setting unit that sets a selected level data from a plurality of level data, based on each of ejecting data forming a row corresponding to a main scanning movement; a driving-signal generator that generates an ejecting-driving signal; a driving-pulse generator that generates a driving pulse based on the selected level data and the ejecting-driving signal; and a main controller that causes the pressure-changing unit to operate, based on the driving pulse; wherein the row of the ejecting data includes: ejecting-sequential data corresponding to a continuous area of level data of relatively high density, an anterior edge data preceding the continuous area, and a posterior edge data following the continuous area; the level-data setting unit is adapted to set a selected level data of relatively high density based on each of the ejecting-sequential data, to set a selected level data of relatively low density based on the anterior edge data, and to set a selected level data of relatively low density based on the posterior edge data.
The above controlling unit or respective components in the controlling unit can be materialized by a computer system.
A program for materializing the respective units or the respective means in the computer system, and a storage medium storing the program capable of being read by a computer, should be protected by the application as well.
The storage unit may be not only a substantial object such as a floppy disk or the like, but also a network for transmitting various signals.